The purpose of embolization is to prevent blood flow to an area of the body, which can effectively shrink a tumor or block an aneurysm, commonly carried out as an endovascular procedure. Access to the organ in question is acquired by means of a guidewire and catheter(s). The position of the correct artery or vein supplying the pathology in question can be located by digital subtraction angiography (DSA), producing images are then used as an accessing map to the correct vessel. The artificial embolus can be made by using coils, particles, foam, plug, microspheres or beads. Once the artificial emboli have been successfully introduced, another set of DSA images are taken to confirm a successful deployment.
Transarterial embolization therapy, tumor embolization, or transcatheter arterial embolization (TAE), involve administration of embolization material (which may include chemotherapeutics or/and radiotherapeutics) directly to a tumor typically associated with a target bodily part, such as an organ (for example, the liver), via a catheter. These techniques are usually performed using a microcatheter which targets the tumor, while attempting to avoid dispersion of embolization material to healthy organs.
Embolization of tumors is usually performed using microcatheters for different reasons. At first, there is a requirement for localized embolization for effecting primarily the tumor and as little healthy tissue as possible. One of the problems associated with embolization is commonly known as “non-target embolization”, where the embolic material travels to small blood vessels other than to those which directly feed the target tumor or region. This can damage healthy tissues in these areas, often resulting in serious complications. Possible scenarios include gastric ulcers with liver embolization, as well as cases where embolic material refluxes alongside the microcatheter reaching the wall of the stomach, possibly causing ischemia and ulceration. An additional phenomenon, which is abundant, especially, in advanced stage liver cancer, is non-target embolization through arterioportal shunt.
A microcatheter is usually passed via a larger-lumen catheter, which is placed within the proximal part of the vessel, such as the celiac or hepatic artery, and the microcatheter is then advanced therethrough towards the tumor until reaching an effective distance for the embolization. It is advantageous to use a diagnostic catheter as the delivery medium for the microcatheter, by not replacing it with a larger diameter sheath, for example, therefore saving substantial time. The inner lumen of the diagnostic catheter is very small, usually 0.035 and up to 0.038 inches, so that the microcatheter should be about 1 mm or less in outer diameter.
Another reason that microcatheters are routinely used in embolization procedures is the size of the feeding vessels, which carry blood directly to the organ and tumor. In order to get as close as possible to the tumor, the embolization catheter is advanced into smaller and sometime tortuous vessels. These vessels cannot be accessed with a larger and often stiffer catheter. Also, blood vessels in the body tend to go into spasm when manipulated, causing an ineffective embolic material delivery, so flexible micro-sized catheters are preferred to avoid such scenarios.